Science of cycling: unsolved mystery

Credit: Woodford, Chris. (2007/2019) Bicycles. explainthatstuff.com

Bicycles are used worldwide and people of various ages for various reasons. People bicycle to work out, commute, deliver packages, compete in races, or just ride for fun. Riding a bicycle might seem easy to some, but it’s actually very complex. Both the rider and the bike play an integral role in the process, which is really more of a science than an art. Every child on himself/herself feels fascinated to be able to ride a bicycle and is always encouraged and helped by his near and dear ones to be able to do it. It is no exaggeration to say that cycling is always a dream come for every child so he spends a lot of time to learn cycling. Most of us know the training we have gone through to be able to cycle.

Starting from a tri-cycle and then with the help of others at one side to finally one day out of blue it happened to be able to balance ourselves on the top of the bicycle. This balancing act comes only by learning to fall and continuous practice with patience without knowing any prescribed procedure.  Once, able to rid the cycle, further balancing techniques of rider make it possible to rid single tier cycle or bicycle with or without using hands, sitting or standing or lying on the top of the cycle as far as cycle is in motion whatever slow it may be. All these acts are possible once the cycle is moving and the science behind the motion of the cycle (balancing) is still a great mystery. With time, there has been a tremendous growth in cycle manufacturing technology and cycles with different characteristics like design, speed, strength, gears, durability, size, light weight and with a low to high range of cost are available in the market but we still don’t really know how bicycles work.

The role of bicycle

If we had to pick the greatest machine of all time, for its sheer simplicity, we would pick the bicycle as a perfect example of how scientific ideas can be harnessed in developing practical applications of technology. Cycles are one of the quick, eeficient and cost effective modes of local transportation without any pollution as well as good for health. They do that because they very efficiently convert the power our bodies produce into kinetic energy (energy of movement). Harnessing the power from our muscles in an

amazingly effective way, a bicycle can convert around 90 percent of the energy we supply at the pedals into kinetic energy that powers us along as compared to a car engine; which converts only about a quarter of the energy of fuel into useful power with all kinds of pollution in the process.   In scientific terms, a bicycle is a machine that can magnify force (making it easier to go uphill) or speed. It's also a machine in the sense that it converts energy from one form (body) into another (the kinetic energy of bicycle). The frame doesn't simply support rider: its triangular shape (often two triangles joined together to make a diamond) is carefully designed to distribute the ride’s weight. Although the saddle is positioned much nearer to the back wheel, we lean forward to hold the handlebars. The angled bars in the frame are designed to share the weight more or less evenly between the front and back wheels. The technology for designing durable, flexible, cost effective different parts of bicycle like: frames, wheels/tires, gears, brakes etc. is well developed and understood and need not to be discussed here.

Science of cycling

People have been making use of bicycle-like machines for nearly two centuries and while riding and balancing a bicycle can seem simple and effort-less, the actual control process used by a rider is still somewhat of a scientific mystery. Making use of mathematical equations, researchers have tried to explain how a bicycle without a rider can balance itself and have identified the bicycle design features critical for that to happen. The ability to remain balanced of a bicycle with a rider is more difficult to quantify and to describe mathematically especially since rider ability can vary widely.  Understanding of scientific concepts behind any action/event makes it easy to repeat the action with more human control and perfection and helps in making the upcoming technology useful for mankind. Man has made tremendous progress in understanding science and developing technology and is looking for mysterious dark matter and the inexplicable accelerating expansion of the universe but the bicycle represents a far more embarrassing hole in the accomplishments of physics. It is common that most people appreciate the bicycle as an extraordinary machine without understanding science behind it. Pushing a riderless bike and letting it roll freely at high enough speeds, it can withstand pushes from the side.  It will wobble a little, but quickly recover. In the conventional analysis, that is because the gyroscopic force of the front wheel, its mass and the spontaneous turn of the handlebars all act together to keep the bicycle rolling forwards. This has something to do with the gyroscopic effect, the force that keeps a spinning top upright. The mathematical analysis of bicycles also suggested that this is what that keeps a moving bike on its wheels. But although the equations were written down in 1910, physicists always had nagging doubts about whether this was the whole story.

The most definitive analysis came exactly a century later which involved an experimental bicycle that had all its gyroscopic effects cancelled out by a system of counter-rotating wheels. It turns out that taking into account the angles of the headset and the forks, the distribution of weight and the handlebar turn, the gyroscopic effects are not enough to keep a bike upright after all and what makes the cycle stand is still not known. Scientists are not taking up the project of finding answer to “what keep a bike upright” because it does attract much attention as people always go by practice themselves to rid the bicycle. However, once we’ve discovered exactly how these contraptions work, it might be possible to come up with bold new designs of bicycle but nobody is desperate for that to happen. In an age where we have worked out the history of the cosmos and the secret of life, it’s rather surprising that the humble bicycle keeps our feet on the ground. The science behind riding – and balancing – a bicycle remains mysterious and scientists have been puzzling over what makes bicycles balance since they were invented, back in the 19th century. In 2007, a group of engineers and mathematicians announced they'd finally cracked the mystery with a set of incredibly complex mathematical equations that explain how a bicycle behaves—and it turns out that gyroscopes are only part of the story. People often say that it's virtually impossible to fall off a bicycle because its spinning wheels make it behave like a gyroscope—but, unfortunately, it's not quite that simple. According to these scientists, who used 25 separate "parameters" or "variables" to describe every aspect of a bicycle's motion, there's no single reason for a bicycle's balance and stability.  A simple explanation to cycle balancing does not seem possible because the action and reaction are coupled by a combination of several effects including: gyroscopic precession, lateral ground-reaction forces at the front wheel ground contact point-trailing behind the steering axis, gravity and inertial reactions from the front assembly having center-of-mass off of the steer axis, and from effects associated with the moment of inertia matrix of the front assembly. In simple terms, it's partly to do with gyroscopic effects, partly to do with how the mass is distributed on the front wheel, and partly to do with how forces act on the front wheel as it spins.

The center of mass is the point at which all the mass (person plus bicycle) can be considered to be concentrated and it is well understood by now that major part of balancing a bicycle can be controlled through the center of mass of the rider-bicycle system. During straight riding, the rider must always keep the center of mass over the wheels or the base of support.  Bicycle riders can use two main balancing strategies i.e., i) steering and ii) body movement relative to the bike. Steering/peddling is critical for maintaining cycling balance and allows the bicycle to move to bring the base of support back under the center of mass. Body movements of rider relative to the bicycle - like leaning left and right - have marginal effect than steering, however, allows a rider to make balance corrections by changing the center of mass side to side relative to the bicycle and base of support. Finally, it can be summarized that steering is absolutely necessary to balance a bicycle, whereas body movements are not and there is no specific combination of the two to ensure balance. The basic strategy to balance a bicycle is to steer into the undesired fall.

Despite much research work in the field, there is still much to be learned about how humans ride and balance bicycles. Most research has been limited to straight line riding, which only makes up a fraction of a typical bicycle ride. Ideally, there is a need to identify the measurements that quantify the balance performance, control strategy and fall risk of a rider in the real world. With deep understanding of the science of cycling, it will be possible to identify riders at high risk of falling and explore the extent to which bicycle design can reduce fall risk and increase balance performance.

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